BY-PRODUCTS TECHNOLOGY

Module 6. Buttermilk

Lesson 43
PHYSICO-CHEMICAL CHARACTERISTICS OF BUTTERMILK AND ITS PRESERVATION

43.1 Introduction

Buttermilk is an important by-product obtained during manufacture of butter. In addition, a substantial amount of lassi (sour buttermilk) is also produced during the manufacture of makkhan directly from fermented milk (curd). Sweet cream buttermilk (SCBM) is almost similar in composition to skim milk except for their high amount of phospholipids and milk fat globular membrane proteins.

43.2 Types of Buttermilk

a) Sweet cream buttermilk obtained by churning of fresh/ pasteurized cream with little or no developed acidity.

b) Sour buttermilk obtained by churning naturally sour milk or cream.

c) Desi buttermilk (lassi) obtained by churning of curd (dahi) during the manufacture of makkhan.

43.3 Chemical Composition of Buttermilk

The chemical composition of buttermilk varies to a great extent, depending on the amount of water added to cream. Some of the butter manufacturers standardize cream with water, thereby decreasing the total solids level of buttermilk. The chemical composition of buttermilk produced under ideal conditions is almost similar to that of skim milk (Table 43.1).

Sour buttermilk differs from sweet cream buttermilk in respect of titratable acidity. The acidity in sweet cream buttermilk varies from 0.10 to 0.14%, whereas in sour buttermilk it is more than 0.15% and even as high as 1%. However, there is not much difference in the chemical composition of two types of buttermilk. Desi buttermilk has wide range of composition depending on the quality of milk used for making curd and levels of addition of water during churning. Desi buttermilk on an average contains 4% total solids comprising of 0.8% fat, 1.29% protein and 1.2% lactic acidity. The colour of desi buttermilk is brownish due to prolonged heating of milk before culturing. When kept undisturbed for sometimes, curdy material deposits at the bottom of desi buttermilk.

Table 43.1 Average gross composition and physico-chemical properties of sweet cream buttermilk and skim milk (obtained from buffalo milk)

43.3.1 Difference between sweet cream buttermilk and skim milk

Buttermilk contains higher fat content than skim milk, which can be reduced to some extent by subjecting it to centrifugal separation. Buttermilk contains a larger proportion of protein mixture sloughed from the fat globule-milk-serum interface by churning process. The amount of fat globule membrane protein (FGMP) is, however, not as large in comparison with total buttermilk proteins. The FGMP are hydrophilic and hydrophobic in nature and their physical properties, nitrogen content and amino acid composition do not correspond with any other milk proteins. These proteins exert emulsion in milk and milk products during manufacture and storage. The FGMP also contributes a complex mixture of glycerophospholipids to buttermilk. Sweet cream buttermilk contains about nine times higher phospholipids than skim milk (Table 43.1). It has been noticed that phospholipids in buttermilk do not have short chain fatty acids. The principal fatty acids are C₁₆ (palmitic) and higher acids. Of the total phospholipid fatty acids, about 40% by wt. are saturated acids and the rest are non-conjugated di- to penta-unsaturated acids. Phospholipids of buttermilk include more or less equal proportions of lecithin, sphingomyelin and cephalin together with a small proportion of cerebrosides.

Various physico-chemical properties of buttermilk also differ from that of skim milk (Table 43.1). These differences in physico-chemical properties of buttermilk and skim milk provide many choices for their selective applications in dairy products manufacture. Buttermilk solids have also been demonstrated to possess antioxidant activity and have been suggested for use in stabilizing food matrixes against lipid peroxidation reactions.

43.4 Buttermilk Powder

Buttermilk can be preserved by converting it in powder form. Production of buttermilk powder from buttermilk follows essentially the same process as the production of skim milk powder from skim milk. The buttermilk is first pasteurized, then concentrated in an evaporator and finally dried (spray or roller dried) to produce buttermilk powder. It shall contain not less than 4.5% milk fat and not more than 5% moisture. It shall have a protein content of not less than 30% and the label should specify the minimum protein content. The phospholipids and total lipid content of dried buttermilk is higher than NFDM. It may not contain or be derived from, skim milk powder, dry whey or products other than buttermilk, and contain no added preservative, neutralizing agent or other chemicals. Heat stability of sweet cream buttermilk is considered to be better than skim milk, thereby making it more suitable for processing to very high heat treatments. The gross composition and physico-chemical properties of spray dried sweet cream buttermilk and skim milk are given in Table 43.2.

Table 43.2 Typical physicochemical characteristics of spray powders

Buttermilk powder is a cream colored powder with a clean, dairy flavor. The solubility of spray dried buttermilk powder is excellent, while the solubility of the roller dried product is not quite as good.

The protein composition of buttermilk powder is essentially the same as skim milk powder with the addition of some protein material originating on the fat globule surface. Sweet cream buttermilk powder has high total lipids including phospholipids than skim milk powder as some small fat droplets are lost to the buttermilk during butter making. Spray dried buttermilk powder has lower bulk density and is less free flowing and dusty because of high fat content in comparison with skim milk powder.

The shelf life of buttermilk powder is 6-9 months and is limited by the potential oxidation of the fat in the powder, which produces an off flavor. Oxidation can be discouraged by main-taining a low moisture content and avoiding exposure of the powder to elements that promote oxidation including light and metals such as copper and iron.

Selected references

Pal, D. and Mulay, C.A. 1983. Influence of buttermilk solids on the physico-chemical and sensory properties of market milks. Asian J. Dairy Res., 2: 129-135.
Pal, D. and Rajorhia, G.S. 1985. Buttermilk utilization in dairy industry. Indian Dairyman, 37 (9): 397-403.